Hi all,

I took my RT out for a run a few weeks ago, after a few weeks standing it was very reluctant to tick over after starting. She eventually ran at a steady idle, so I went out for a run. The bus struggled on a hill it normally begins in 3rd gear and finishes in second. This hill is a similar gradient to London's Muswell Hill managed by generations of London buses - though longer. Only this occasion though I had to start the hill in second and only just finished in first. I expected a braekdown at this point - the bus exhaust was also very smokey.

Last Sunday I started the bus, she started first time, a very slow idle even with the peddle down, and she soon cut out and would not re-start.

I suspect a filter blockage? There is the main 'cannister' filter I see, but is there a thimble size filter for example it the lift pump?

Which is the first port of call, and is the filter in the cannister (main filter) a throw away, and if so where can I obtain a new one (part name/number?). My bus is an AEC type.

Thank you
John

The main fuel tank, because that's where the problems originate. Then the bulkhead tank which will also be full of crap. Once they are CLEAN and all the fuel lines are CLEAN then you will know that you aren't wasting your time cleaning the filters, one of which is under the bus on the chassis n/s side member. The main fuel filter will be a cloth wrapped around a cage. Unless you are very lucky you will not find a replacement so it will have to go in the washing machine.

The rack occasionally sticks if the engine hasn't been run for some time.

Thank you for that Roy. I daresay that there will certainly be crap in the fuel tank, this was the cause of a breakdown on my first RM - my one and only RM breakdown having owned 7 RMs over the years.

You talk of the 'rack' sticking, can you be more specific on this bearing in mind that I am not a trained fitter with buses, but more familiar with old cars. Also, cleaning the tank, I assume means removing the drain plate, though I do not have an air line to blast things out.

John

Removing the bung from the bottom of the main fuel tank after the vehicle has been stood for 24 hrs should give some idea of what condition the tank is in. There is a reasonable chance that the system is contaminated with diesel bug, which you can Google. To clean the tank(s) out properly means draining and removing them so that the inside can be seen. Only a small portion of the tank can be seen from the filler neck when in situ. More than likely there will be a layer of sludge clinging to the bottom which will also probably be pitted and rusty. This gets drawn into the pipework and trapped at right angle bends or in joining unions. The tanks are probably best cleaned out with a steam cleaner and then dealt with according to the extent of corrosion. There are various chemical treatments available for old fuel tanks - you will need to research fully the pros and cons of their use. Traditional radiator overhaul companies are generally able to fabricate new fuel tanks.

There should be an additional filter in the inlet union of the injector pump. There should also be a filter on the end of the pick up pipe in the main fuel tank. There is a ball seat on/off valve in the bulkhead tank.

The rack is inside the injector pump. On the side of the pump is a large plate secured with three slot-head screws. Remove this and inside can be seen the quadrants which are rotated by the rack. This should move to and fro freely by finger pressure alone.
Below this plate is the oil filler plug for the pump and beside it is the dipstick. Below that is the cambox drain plug. On the top of the Governor housing is its oil filler plug. Towards the bottom of the governor housing below the throttle shaft is the level plug for the governor. Use engine oil.

That is all of great help and interest, Roy. Your time has not gone unappreciated. Because it was easy to get at, while down where the bus is parked today, I went in and took the main fuel filter out. It is cloth covered as you said, and the colour of a used teabag, but originaly white I suppose?

Loads of crud, and the cloth is well clogged up. I will do the other filters as soon as I am back there with some time. I shall then check the injector pump as your description. If the lines are clear, and this gets the vehicle running I will probably take the bus to a set-up that can remove the main tank and have it cleaned. I should be able to manage the bulkhead tank. Where I keep the bus has little provision for removing large items like the tank, and the bus needs to be kept as mobile as possible due to space restrictions.

These things all seem to come along at once (just like the proverbial bus). Last week I had to make a new floor for the battery compartment. Not much left of the original, with the possibility of the batteries falling through. Fortunately the metal holding cradle seems sound.

John

I can supply a filter cloth if you feel you still need one after you've done everything roy suggested.

Don't throw out the old one, you need to work out how it's folded.

Dave - I could do with one or two of those filters the next time I see you (which I need to arrange sooner rather than later). The filter in my header tank is of the sheer dernier type (one leg only)!

Rattlesnake/rattleshake (or whatever your name is) - With regards to fuel blockage, my personal experience from a couple of years ago indicates to me that your problem is not directly to do with the fuel tank or fuel lift pump, but at the header tank / injector end.

I had a fuel blockage that was starving my RT of fuel from the tank. When idling, a little fuel would get through, but when accelerating none would get through at all. I was unaware that this was the case until we dismantled the fuel delivery system.

The fuel is pulled up from the tank by a fuel lift pump accessible through the centre floor trap. It can be clearly seen with fuel pipes going to and from it, but is really only accessed from below. The fuel is pumped to the header tank where it passes through the filter and is then gravity fed to the injectors.

My blockage was between the lift pump and main tank and was 'cleared' by use of an air line. I say 'cleared', because all we have done is push the problem back into the tank, but it resolved it.

The behaviour with my blockage was that the bus started, idled and ran perfectly. As long as I kept adding fuel to the header tank, the running was fine. I could barely travel a dozen miles without having to add more fuel, but there was no sluggishness.

Hopefully this helps you narrow down your troubleshooting before you go and remove the tank, find it impossible to get properly clean for less than the cost of a new one, only to find out that the problem lies at the front of the bus.

Steve

My bus number (if any): RT3316

I certainly would not dispute that the bulkead gravity tank causes problems similar to the descriptions and that it is a lot easier to remove. It is also considerably easier and cheaper if the fault lies in the fuel pipes. However from your account Steve and the admission, you have merely returned the problem to the main fuel tank to reappear at a later date. From looking at your blog I can only say that if the bus was mine and I was paying the bills , I would be removing the main tank while the outer panels are off.

Going from past quotes for a smaller tank I would estimate that a newly constructed tank should it be needed, will cost in the region of £700 - £1200 maybe less. This is a considerable sum, but it can be made from readily available materials. The CAV BPE6B and Simms SPE6B fuel injection pumps have been obsolete for the past 50 years. Parts for these are like hen's teeth with some items simply unobtainable. The amount of work involved to overhaul one of these properly is extensive, one can judge the result from the price quoted. It will of course be the FIP that suffers from dirt and water ingress. More seriously diesel bug, which breeds in fuel tanks and particularly tanks with standing fuel, corrodes the fuel injection system with those hard to obtain parts.

Cleaning out the fuel tank(s) may seem to be overkill, but the neglect of suchlike it is good business for fuel injection specialists. The gum and varnish that develop inside injection pumps which are running on clean diesel cause enough problems without adding other contaminants.

Surely it would be prudent to keep the level of fuel in the main tank high so as to avoid the lift pump dragging up sludge from the tank floor. At least until the tank has been cleaned out or replaced.

My bus number (if any): Searching for a driving RT or RM

On the RT I have in my workshop at the moment there is a small filter on the chassis that should be cleaned out. Parts for these are still available, though the metal gauze filters are now nylon gauze.

I had an RT in for a customer about 20 years ago that had similar problems. Lack of power, sluggish, would run out of fuel every 10 miles or so. I changed the injectors, that took 3 days freeing them off and removing them; changed the filter cloth and cleaned the intermediate filter mentioned above. Test run, it was ok, but ran out of fuel every 10 miles. So I removed fuel pipes and blew them through with compressed air. they were ok. Test run again, same problem.

Eventually I gave up and handed the bus back to the owner. He phoned me a while after to tell me he still had the problem, but had found it. While the pipes would pass compressed air and a small amount of fuel, they would not pass enough to run the bus. He rodded the pipes through and found a yellowy treacle stuck inside the pipes. After that the problem went away. Of course on the RT the header tank only fills while the bus is moving, and the header tank takes about a gallon, and the bus does 8mpg, hence it ran out of fuel every 8 miles!

There was a similar problem on an RT in Germany, it wouldn't start. I went over and found they'd run the engine for over an hour in the garage trying to sort another problem and the header tank emptied itself!

I've had the same problem on an RM on the return pipe from the spill-off to the tank, where we would get an awful smell of diesel under certain circumstances. We replaced the pipe with a bit of flexible and problem solved.

If rattletrap is interested, I have a couple of overhauled RT fuel pumps for sale as well as overhauled injectors.

Personally I don't think running the tank low allows sludge to be picked up, the sludge is there anyway whatever the fuel level. some schools of thought suggest the opposite especially as it seems diesel bug grows better in full tanks. Maybe someone with a better understanding of that problem knows better.

Edited to add my RT2629 failed to start having sat around for about 15 years. The fuel pump rack is jammed solid, so I'll have to replace the pump. What causes the rack to jam is the plungers get a small amount of water in them and fail to move, and this causes the rack to stick.

My bus number (if any): RML2532

Hi Roy.
With interest in reference regarding your piece about RM return pipe.
I have RML with Scania engine. On cold start up we often get a smell
More like rotten eggs & often on over run when running warm. (coming off
throttle at junctions etc)
I have also removed the cat. Replaced filters, cleaned tank.
Does this sound like your problem in respect of return pipe.
Appreciate your thoughts.
Regards
Brian.

My bus number (if any): RML2616

It's Rattletrap, Steve - that is the name I have for my bus, 'Rattletrap RT', which I think suits it, especially at the moment! Google Rattletrap to see description...


Well, very interesting replies from everyone, with varying opinions! I am concerned that I with my minimum knowledge/experience of RTs - than many of you with far greater experience of these buses but still, even so differ in opinion - may well be set to have an uphill struggle. None the less I will plough on. I would have thought that there would be a small filter before the lift pump fuel inlet, and thus the first place to investigate?

Having said that, when I removed the main filter cannister to take out the filter, it was brim to the top with fuel, whereas I expected to it be empty???

John

My bus number (if any): Rattletrap RT

The small chassis mounted filter IS between the main tank and the lift pump and yes it is the first to block up, as are the unions in its filter head. I would expect you to find contamination inside it, if it actually has an element inside that is - it being not unknown for people to throw filter elements away.

So, what to do? check this filter then look in the tank with a torch, after that undo the drain plug carefully and drain a gallon out of the main tank into a clean container which is capable of holding at least two gallons. When that has settled you will know what you are up against. You can do the same thing with the bulkhead tank.

Batteries overcharging smell like rotten eggs. Occasionally these days we encounter a car which is burning oil and recognise the smell. What we don't seem to come across these days any longer, although it used to be common on the downhill Motorway banks, is the smell of a large diesel engine doing the same thing, which is a very distinctive smell. The other smell which is not so common these days is crankcase fumes from the engine breather.

The return pipe problem was the smell of leaking diesel, but we never found where it was leaking from! It may have entered the fuel pump on the AEC engine vi the spill-off pipe then into the sump via the governor box overflow.

My bus number (if any): RML2532

Hi gents,
Thanks for your comments.
I shall have to keep smelling & try to work out where it comes from.
Engine doesn't breathe when warm out of oil filler cap or sump breather pipe.
The smell is when engine warm & cold.
Someone mentioned to me the cat could
Have impregnated the exhaust system so may have to change full system.
Regards Brian
RML2616

My bus number (if any): RML2616

I do find it a worry that people can buy an old bus, not having a comprehensive mechanical knowledge and drive it on the public road.

More so that the oldest vehicles do not have to have an MOT test.

My bus number (if any): Looking to buy

There's no requirement for anyone who drives to know much mechanical. What every preserved bus owner should have is someone who DOES know about such things and gets a regular safety check on the bus.

My bus number (if any): RML2532

Unfortunately, not everyone with expert bus knowledge is interested in preserving vintage buses, just as not everyone without knowledge is not interested in these wonderful old vehicles.

Whatever our abilities and facilites, we all have the same goal here - to keep the remaining RTs and RMs alive.

So to my next question that shows I am still learning with my RT. I assume that the handle on top of the fuel header tank is the fuel shut off only. I do not see a hand primer pump.

With fuel flow open, am I right that this handle is up and facing forward to the radiator, and down facing away for fuel shut off?

John

My bus number (if any): Rattletrap RT

So on the header fuel tank, is it okay to remove the large nut on the top right side and pour in diesel, so as to fill it direct, and help me fire the engine up even with a possible blockage further back to the main tank?

I don't want the bus standing for a period of time before I sort out the fuel blockage issues. I have had the main filter out, and with the use of printer's machine blanket and roller wash, (this is strong stuff), have got the filter to a state where you can see day light when looking inside, and diesel now passes through. But I have yet to try to start the bus, so a blockage could exist before the header tank, as some here think likely.

John

It could be that the diesel in the tank has started waxing. It's also possible it is contaminated. So better to drain the entire system from the tank and remove and clean the entire system as components. Safer as away from the bus and easier to inspect each item.
Be very careful what you use as some modern cleaners can dissolve soldered and braised joints or trigger corrosion. Some are combustible and produce toxic vapours so ventilation and spark free working environment necessary. Make sure you know the flash point and compression flash point of what you use.

A feed hose line from a 1 gallon tank fed into the final line to the injectors should get it running.

Yes, the RT in my garage has the tank off at the moment but still runs in and out of the shed using the fuel in the header tank.

My bus number (if any): RML2532

Don't worry yourself too much, I've had a crack at my RT's apparent fuel problem. However, to no avail. I do not have the facility for any comprehensive stripping if the fuel system, nor sufficient knowledge or any experience before with such a problem.

Any one here interested in a trip to north London, expenses paid to have a go at this?

Reply by email please
John

My bus number (if any): Rattletrap RT

What is it you want done, do you have facilities for getting under the bus such as a pit or lifts? Like a lot on here, I'm getting beyond the stage of crawling under buses on the ground and advancing years mean I need additional ground clearance!

I still go out as "man and van" to do repairs, yesterday it was to Welham Green to sort a brake problem on a routemaster for someone.

Send me an email if you're interested.

My bus number (if any): RML2532

In the LT operating days of yesteryear, a GSI (General Service Instruction) was issued to all garages that on the onset of winter all fuel chassis filters elements be removed and replaced at the advent of spring.

The positioning of this filter mounted on the chassis was exposing it to all the elements that winter could give.

These filters were constructed of a fine metal gauze, slowing the flow of fuel which now froze, causing a wax residue to form around the element therefore causing fuel starvation.

No problem for the running shift to attend on callout.
One man with a replacement bus for the crew, and a dummy header tank to get home.

I would suggest it be prudent for all RT vintage bus owners in this day and age, to possess a small tank for such use.

My bus number (if any): Ex LTE Bus Engineering

I've fiddled about, cleaned the filter and drained and refilled the head fuel tank. After some bleeding at the business end, she seems to be running?

However, I have no breakdown cover at the moment, so dare not go out on the road. I know Rigton can provide breakdown cover - but not for a day only. I will not be using the bus other than say, for a day a month. Who do people here have their breakdown cover with - do you have to pay a lump sum for a whole year, or do you get cover as requested for the odd run? Similarly, who else other than Rigton does bus insurance at a reasonable rate?

John

My bus number (if any): Rattletrap RT

I don't think the Rigtons breakdown scheme is unreasonable at a bout £89 a year. A lot of us only use their buses a few times a year. Otherwise you're looking at a minimum of about £280 for a tow truck from a breakdown company.

Take a couple of gallons of spare fuel with you, if the fuel system fails, fill the header tank and off you go again...unless the injection pump fails, which is also a possibility for a bus that has stood for years.

My bus number (if any): RML2532